Re: [PATCH 4/4] iio: ti_am335x_adc: Add continuous sampling and trigger support

On Fri, Aug 16, 2013 at 03:25:49PM +0200, Sebastian Andrzej Siewior wrote:

* Zubair Lutfullah | 2013-08-13 21:05:03 [+0100]:

quoted

diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c
index 3ceac3e..0d7e313 100644
--- a/drivers/iio/adc/ti_am335x_adc.c
+++ b/drivers/iio/adc/ti_am335x_adc.c

@@ -141,58 +350,51 @@ static int tiadc_read_raw(struct iio_dev *indio_dev,

{

…

quoted

+	if (iio_buffer_enabled(indio_dev))
+		return -EBUSY;
+	else {

You can drop else so you lose one ident level.

Noted.

quoted

+		unsigned long timeout = jiffies + usecs_to_jiffies
+					(IDLE_TIMEOUT * adc_dev->channels);

What computing this once? ->channels is assigned at probe time.

The timeout depends on number of SW enabled channels.
Hence the calculation. In this read_raw, one channel is to be
read. 
However, all channels are sampled. And the one that the 
userspace requires is pushed to user.

quoted

+		/* Wait for ADC sequencer to complete sampling */
+		while (tiadc_readl(adc_dev, REG_ADCFSM) & SEQ_STATUS) {
+			if (time_after(jiffies, timeout))
+				return -EAGAIN;

You should check the condition after the timeout occured once again. It
is possible that the task performing the read has been pushed away by a
higher prio task (or preempted incase this sounds like a bully) and
after it got back on the cpu the timeout occured but the condition is
valid and no reason for -EAGAIN.

Sebastian

Interesting catch. I'll look into it.

Thanks for pointing it out.

Zubair